Use the tonic namespace for tonic + resulting build fixes

tonic/dart_persistent_value.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tonic/dart_persistent_value.h"
 
 #include "tonic/dart_isolate_scope.h"
 #include "tonic/dart_state.h"
 
-namespace blink {
+namespace tonic {
 
 DartPersistentValue::DartPersistentValue() : value_(nullptr) {
 }
 
 DartPersistentValue::DartPersistentValue(DartState* dart_state,
                                          Dart_Handle value)
     : value_(nullptr) {
   Set(dart_state, value);
 }
 
@@ skipping 18 matching lines @@
 }
 
 Dart_Handle DartPersistentValue::Release() {
   if (!value_)
     return nullptr;
   Dart_Handle local = Dart_HandleFromPersistent(value_);
   Clear();
   return local;
 }
 }